Chemical mechanical polishing pad

ABSTRACT

The polishing pad is for polishing patterned semiconductor substrates. The pad includes a polymeric matrix and hollow polymeric particles within the polymeric matrix. The polymeric matrix is a polyurethane reaction product of a curative agent and an isocyanate-terminated polytetramethylene ether glycol at an NH 2  to NCO stoichiometric ratio of 80 to 97 percent. The isocyanate-terminated polytetramethylene ether glycol has an unreacted NCO range of 8.75 to 9.05 weight percent. The hollow polymeric particles having an average diameter of 2 to 50 μm and a wt % b  and density b  of constituents forming the polishing pad as follows: 
     
       
         
           
             
               
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     where density a  equals an average density of 60 g/l, where density b  is an average density of 5 g/l to 500 g/l, where wt % a  is 3.25 to 4.25 wt %. The polishing pad has a porosity of 30 to 60 percent by volume; and a closed cell structure within the polymeric matrix forms a continuous network surrounding the closed cell structure.

BACKGROUND

This specification relates to polishing pads useful for polishing orplanarizing semiconductor substrates. The production of semiconductorstypically involves several chemical mechanical polishing (CMP)processes. In each CMP process, a polishing pad in combination with apolishing solution, such as an abrasive-containing polishing slurry oran abrasive-free reactive liquid, removes excess material in a mannerthat planarizes or maintains flatness for receipt of a subsequent layer.The stacking of these layers combines in a manner that forms anintegrated circuit. The fabrication of these semiconductor devicescontinues to become more complex due to requirements for devices withhigher operating speeds, lower leakage currents and reduced powerconsumption. In terms of device architecture, this translates to finerfeature geometries and increased numbers of metallization levels. Theseincreasingly stringent device design requirements are driving theadoption of smaller and smaller line spacing with a correspondingincrease in pattern density. The devices' smaller scale and increasedcomplexity have led to greater demands on CMP consumables, such aspolishing pads and polishing solutions. In addition, as integratedcircuits' feature sizes decrease, CMP-induced defectivity, such as,scratching becomes a greater issue. Furthermore, integrated circuits'decreasing film thickness requires improvements in defectivity whilesimultaneously providing acceptable topography to a wafer substrate;these topography requirements demand increasingly stringent planarity,line dishing and small feature array erosion polishing specifications.

Historically, cast polyurethane polishing pads have provided themechanical integrity and chemical resistance for most polishingoperations used to fabricate integrated circuits. For example,polyurethane polishing pads have sufficient tensile strength andelongation for resisting tearing; abrasion resistance for avoiding wearproblems during polishing; and stability for resisting attack by strongacidic and strong caustic polishing solutions. Unfortunately, the hardcast polyurethane polishing pads that tend to improve planarization,also tend to increase defects.

M. J. Kulp, in U.S. Pat. No. 7,169,030, discloses a family ofpolyurethane polishing pads having high tensile modulus. These polishingpads provide excellent planarization and defectivity for severalcombinations of polishing pads and polishing slurries. For example,these polishing pads can provide excellent polishing performance forceria-containing polishing slurries, for polishing silicon oxide/siliconnitride applications, such as direct shallow trench isolation (STI)polishing applications. For purposes of this specification, siliconoxide refers to silicon oxide, silicon oxide compounds and doped siliconoxide formulations useful for forming dielectrics in semiconductordevices; and silicon nitride refers to silicon nitrides, silicon nitridecompounds and doped silicon nitride formulations useful forsemiconductor applications. Unfortunately, these pads do not haveuniversal applicability for improving polishing performance with allpolishing slurries for the multiple substrate layers contained intoday's and future semiconductor wafers. Furthermore, as the cost ofsemiconductor devices decreases, there remains a need for further andfurther increases in polishing performance.

Increasing a polishing pad's removal rate can increase throughput todecrease a semiconductor fabrication plant's equipment footprint andexpenditure. Because of this demand for increasing performance, thereremains a desire for a polishing pad to remove substrate layers withincreased performance. For example, oxide dielectric removal rates areimportant for removing dielectrics during inter-layer dielectric (“ILD”)or inter-metallic dielectric (“IMD”) polishing. Specific types ofdielectric oxides in use include the following: BPSG, TEOS formed fromthe decomposition of tetraethyloxysilicates, HDP (“high-density plasma”)and SACVD (“sub-atmospheric chemical vapor deposition”). There is anongoing need for polishing pads that have increased removal rate incombination with acceptable defectivity performance and waferuniformity. In particular, there is a desire for polishing pads suitablefor ILD polishing with an accelerated oxide removal rate in combinationwith acceptable planarization and defectivity polishing performance.

STATEMENT OF INVENTION

The invention provides a polishing pad suitable for polishing patternedsemiconductor substrates containing at least one of copper, dielectric,barrier and tungsten, the polishing pad comprising a polymeric matrixand hollow polymeric particles within the polymeric matrix, thepolymeric matrix being a polyurethane reaction product of a curativeagent and an isocyanate-terminated polytetramethylene ether glycol at anNH₂ to NCO stoichiometric ratio of 80 to 97 percent, theisocyanate-terminated polytetramethylene ether glycol having anunreacted NCO range of 8.75 to 9.05 weight percent, the curative agentcontaining curative amines that cure the isocyanate-terminatedpolytetramethylene ether glycol to form the polymeric matrix; and thehollow polymeric particles having an average diameter of 2 to 50 μm anda wt %_(b) and density_(b) of constituents forming the polishing pad asfollows:

$\frac{{wt}\mspace{14mu} \%_{a}*{density}_{b}}{{density}_{a}} = {{wt}\mspace{14mu} \%_{b}}$

where density_(a) equals an average density of 60 g/l,where density_(b) is an average density of 5 g/l to 500 g/l,where wt %_(a) is 3.25 to 4.25 wt %,the polishing pad having a porosity of 30 to 60 percent by volume and aclosed cell structure within the polymeric matrix forming a continuousnetwork surrounding the closed cell structure.

Another embodiment of the invention provides a polishing pad suitablefor polishing patterned semiconductor substrates containing at least oneof copper, dielectric, barrier and tungsten, the polishing padcomprising a polymeric matrix and hollow polymeric particles within thepolymeric matrix, the polymeric matrix being a polyurethane reactionproduct of a curative agent and an isocyanate-terminatedpolytetramethylene ether glycol at an NH₂ to NCO stoichiometric ratio of80 to 90 percent, the isocyanate-terminated polytetramethylene etherglycol having an unreacted NCO range of 8.75 to 9.05 weight percent, thecurative agent containing curative amines that cure theisocyanate-terminated polytetramethylene ether glycol to form thepolymeric matrix; and the hollow polymeric particles having an averagediameter of 2 to 50 μm and a wt %_(b) and density_(b) of constituentsforming the polishing pad as follows:

$\frac{{wt}\mspace{14mu} \%_{a}*{density}_{b}}{{density}_{a}} = {{wt}\mspace{14mu} \%_{b}}$

where density_(a) equals an average density of 60 g/l,where density_(b) is an average density of 10 g/l to 300 g/l,where wt %_(a) is 3.25 to 3.6 wt %,the polishing pad having a porosity of 35 to 55 percent by volume and aclosed cell structure within the polymeric matrix forming a continuousnetwork surrounding the closed cell structure.

DESCRIPTION OF THE DRAWING

FIG. 1 is a 250× magnification post-polishing scanning electronphotomicrograph of the polishing surface of a pad of the invention.

FIG. 2 is a 500× magnification post-polishing scanning electronphotomicrograph of the polishing surface of a pad of the invention.

FIG. 3 is a 500×EDS image of the polishing pad of FIGS. 1 and 2, in thesame region as FIG. 2, illustrating a high concentration of siliconafter polishing with a silica-containing polishing slurry.

DETAILED DESCRIPTION

The invention provides a polishing pad suitable for planarizing at leastone of semiconductor, optical and magnetic substrates, the polishing padcomprising a polymeric matrix. The polishing pads are particularlysuitable for polishing and planarizing ILD dielectric materials as ininter-layer dielectric (ILD) applications, but could also be used forpolishing metals such as copper or tungsten. The pad provides increasedremoval rate over current pads—especially in the first 30 seconds ofpolishing. The accelerated response of the pad during the early part ofpolishing makes possible increased wafer throughput by shortening neededpolishing time to remove a specified amount of material from a wafersurface.

The removal rate for ILD polishing with fumed silica at 30 seconds canbe greater than 3750 Å/minute. Furthermore, the invention may provide atleast a 10% higher removal rate than the removal rate at 30 secondsgiven by IC 1010™ polyurethane polishing pads in the same polishingtest. (IC1010 is a trademark of Rohm and Haas Company or itsaffiliates.) Advantageously, the removal rate for the polishing pads ofthe invention at thirty seconds for polishing TEOS sheet wafers with asilica-containing abrasive is equal to or greater than the removal ratefor IC1000 polishing pads for polishing TEOS sheet wafers with asilica-containing abrasive at both thirty and sixty seconds. IC1000™ mayincrease TEOS removal rate with polishing time because it comprisesaliphatic isocyanate that tends to impart thermoplastic character toparts made from the ingredients. (IC1000 is a trademark of Rohm and HaasCompany or its affiliates.) The thermoplastic character of IC1000polishing pads appears to facilitate an increase in contact between thepolishing pad and the wafer along with an increase in removal rate untilsome maximum in removal rate occurs. Increasing pad to wafer contactarea to ever higher levels appears to decrease removal rate as thelocalized asperity to wafer contact pressure decreases. Similarly,formulations not comprising aliphatic isocyanate will have morethermoplastic character as the degree of cross-linking or molecularweight decreases; and they may show more of an increase in removal ratewith a wafer's polishing time. The pad of the invention, however, hassufficient levels of porosity to maximize pad to wafer contact veryearly in the polishing process; and the relatively high level ofcross-linking appears to provide the pad sufficient localized stiffnessto facilitate the polishing process.

Although removal rate can increase with abrasive content, an improvementover IC1010 polishing pad's removal rate independent of abrasive levelrepresents an important advance in polishing performance. For example,this facilitates increasing removal rate with low defectivity and maydecrease slurry costs. In addition to removal rate, wafer-scalenonuniformity also represents an important polishing performanceconsideration. Typically, because polished wafer uniformity is importantfor getting the maximum number of well-polished dies, the wafer-scalenonuniformity should be less than 6%.

For purposes of this specification, “polyurethanes” are products derivedfrom difunctional or polyfunctional isocyanates, e.g. polyetherureas,polyisocyanurates, polyurethanes, polyureas, polyurethaneureas,copolymers thereof and mixtures thereof. Cast polyurethane polishingpads are suitable for planarizing semiconductor, optical and magneticsubstrates. The pads' particular polishing properties arise in part froma prepolymer reaction product of a prepolymer polyol and apolyfunctional isocyanate. The prepolymer product is cured with acurative agent selected from the group comprising curative polyamines,curative polyols, curative alcohol amines and mixtures thereof to form apolishing pad. It has been discovered that controlling the ratio of thecurative agent to the unreacted NCO in the prepolymer reaction productcan improve porous pads' defectivity performance during polishing.

The urethane production involves the preparation of anisocyanate-terminated urethane prepolymer from a polyfunctional aromaticisocyanate and a prepolymer polyol. The prepolymer polyol ispolytetramethylene ether glycol [PTMEG]. Example polyfunctional aromaticisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate,4,4′-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate,tolidine diisocyanate, para-phenylene diisocyanate, xylylenediisocyanate and mixtures thereof. The polyfunctional aromaticisocyanate contains less than 20 weight percent aliphatic isocyanates,such as 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanateand cyclohexanediisocyanate. Preferably, the polyfunctional aromaticisocyanate contains less than 15 weight percent aliphatic isocyanatesand more preferably, less than 12 weight percent aliphatic isocyanate.

Typically, the prepolymer reaction product is reacted or cured with acurative amine such as a polyamine or polyamine-containing mixture. Forexample, it is possible to mix the polyamine with an alcohol amine or amonoamine. For purposes of this specification, polyamines includediamines and other multifunctional amines. Example curative polyaminesinclude aromatic diamines or polyamines, such as,4,4′-methylene-bis-o-chloroaniline [MBCA],4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) [MCDEA];dimethylthiotoluenediamine; trimethyleneglycol di-p-aminobenzoate;polytetramethyleneoxide di-p-aminobenzoate; polytetramethyleneoxidemono-p-aminobenzoate; polypropyleneoxide di-p-aminobenzoate;polypropyleneoxide mono-p-aminobenzoate;1,2-bis(2-aminophenylthio)ethane; 4,4′-methylene-bis-aniline;diethyltoluenediamine; 5-tert-butyl-2,4- and3-tert-butyl-2,6-toluenediamine; 5-tert-amyl-2,4- and3-tert-amyl-2,6-toluenediamine and chlorotoluenediamine. A MBCA additionrepresents the preferred curative amine. Optionally, it is possible tomanufacture urethane polymers for polishing pads with a single mixingstep that avoids the use of prepolymers.

The components of the polymer used to make the polishing pad arepreferably chosen so that the resulting pad morphology is stable andeasily reproducible. For example, when mixing4,4′-methylene-bis-o-chloroaniline [MBCA] with diisocyanate to formpolyurethane polymers, it is often advantageous to control levels ofmonoamine, diamine and triamine. Controlling the proportion of mono-,di- and triamines contributes to maintaining the chemical ratio andresulting polymer molecular weight within a consistent range. Inaddition, it is often important to control additives such asanti-oxidizing agents, and impurities such as water for consistentmanufacturing. For example, because water reacts with isocyanate to formgaseous carbon dioxide, controlling the water concentration can affectthe concentration of carbon dioxide bubbles that form pores in thepolymeric matrix. Isocyanate reaction with adventitious water alsoreduces the available isocyanate for reacting with chain extender, sochanges the stoichiometry along with level of crosslinking (if there isan excess of isocyanate groups) and resulting polymer molecular weight.

The polyurethane polymeric material is preferably formed from aprepolymer reaction product of toluene diisocyanate withpolytetramethylene ether glycol and an aromatic diamine. Most preferablythe aromatic diamine is 4,4′-methylene-bis-o-chloroaniline or4,4′-methylene-bis-(3-chloro-2,6-diethylaniline). Preferably the rangeof unreacted prepolymer % NCO is 8.75-9.05. A particular example of asuitable prepolymer within this unreacted NCO range is Adiprene®prepolymer LF750D manufactured by Chemtura. In addition, LF750Drepresents a low-free isocyanate prepolymer that has less than 0.1weight percent each of free 2,4 and 2,6 TDI monomers and has a moreconsistent prepolymer molecular weight distribution than conventionalprepolymers. This “low-free” prepolymer with improved prepolymermolecular weight consistency and low free isocyanate monomer facilitatesa more regular polymer structure, and contributes to improved polishingpad consistency. In addition to controlling weight percent unreactedNCO, the curative and prepolymer reaction product typically has an OH orNH₂ to unreacted NCO stoichiometric ratio of 80 to 97 percent,preferably 80 to 90 percent; and most preferably, it has an OH or NH₂ tounreacted NCO stoichiometric ratio of 83 to 87 percent. It is possibleto achieve this stoichiometry either directly, by providing thestoichiometric levels of the raw materials, or indirectly by reactingsome of the NCO with water, either purposely or by exposure toadventitious moisture.

If the polishing pad is a polyurethane material, then the finishedpolishing pad preferably has a density of 0.4 to 0.8 g/cm³. Mostpreferably, the finished polyurethane polishing pads have a density of0.5 to 0.75 g/cm³. A hollow polymeric particle loading density (beforecasting) of 3.25 to 4.25 weight percent and preferably 3.25 to 3.6weight percent of the nominal 20 μm pores or hollow polymeric particlesbased on the total pad formulation can produce the desired density withexcellent polishing results. In particular, the hollow polymericparticles provide a random pore distribution throughout the polymermatrix. In particular, the polishing pad has a closed cell structurewith the polymeric matrix forming a continuous network surrounding theclosed cell structure. Despite this high porosity, the polishing padtypically has a Shore D hardness of 44 to 54. For purposes of thespecification, the Shore D test includes conditioning pad samples byplacing them in 50 percent relative humidity for five days at 25° C.before testing and using methodology outlined in ASTM D2240 to improvethe repeatability of the hardness tests.

The hollow polymeric particles have a weight average diameter of 2 to 50μm. For purposes of the specification, weight average diameterrepresents the diameter of the hollow polymeric particle before casting;and the particles may have a spherical or non-spherical shape. Mostpreferably, the hollow polymeric particles have a spherical shape.Preferably, the hollow polymeric particles have a weight averagediameter of 2 to 40 μm. Most preferably, the hollow polymeric particleshave a weight average diameter of 10 to 30 μm; these hollow polymericparticles typically have an average density of 60 grams per liter. Forpurposes of this specification, average density of the hollow polymericparticles represents the close-packed-non-crushed density of the hollowparticles within a one liter volume. Hollow particles with an averagediameter of 35 to 50 μm typically have lower density averaging 42 gramsper liter because there are fewer pores and less wall material. Hollowparticles of different sizes and types can be added at equivalent porevolumes by taking the mass of the hollow polymeric particles of one sizeand dividing by their density to determine the volume of pores. Thisvolume can then be multiplied by the density of the other pore todetermine the mass of the hollow polymeric particles of that size andtype to give equivalent pore volume For example, a formulation with 3 wt% of 20 μm hollow polymeric particles with a density of 60 grams perliter would be equivalent to 2.1 wt % of 42 μm hollow polymericparticles with a density of 40 grams per liter as shown by the equationthat follows.

$\frac{{wt}\mspace{14mu} \%_{a}*{density}_{b}}{{density}_{a}} = {{wt}\mspace{14mu} \%_{b}}$

In forming polishing pads of the invention, density_(a) equals anaverage density of 60 g/l, density_(b) is an average density of 5 g/l to500 g/l and wt %_(a) is 3.25 to 4.25 wt %. Preferably, density_(b) is anaverage density of 10 g/l to 150 g/l and wt %_(a) is 3.25 to 3.6 wt %.

The nominal range of expanded hollow-polymeric particles' weight averagediameters is 15 to 90 μm. Furthermore, a combination of high porositywith small pore size can have particular benefits in reducingdefectivity. If the porosity level becomes too high, however, thepolishing pad loses mechanical integrity and strength. For example,adding hollow polymeric particles of 2 to 50 μm weight average diameterconstituting 30 to 60 volume percent of the polishing layer facilitatesa reduction in defectivity. Furthermore, maintaining porosity between 35and 55 volume percent or specifically, 35 and 50 volume percent canfacilitate increased removal rates. For purposes of this specification,volume percent porosity represents the volume percent of poresdetermined as follows: 1) subtracting the measured density of theformulation from the nominal density of the polymer without porosity todetermine the mass of polymer “missing” from the a cm³ of formulation;then 2) dividing the mass of “missing” polymer by the nominal density ofthe polymer without porosity to determine the volume of polymer missingfrom a cm³ of formulation and multiplying by 100 to convert it to aporosity volume percentage. Alternatively, the volume percent of poresin a formulation or volume percent porosity can be determined asfollows: 1) subtracting the mass of hollow polymeric particles in 100 gformulation from 100 g to determine the mass of polymer matrix in 100 gof formulation; 2) dividing the mass of polymer matrix by the nominaldensity of the polymer to determine the volume of polymer in 100 g offormulation; 3) dividing the mass of hollow polymeric particles in 100 gof formulation by the nominal hollow polymeric particle density todetermine the volume of hollow polymeric particles in 100 g offormulation; 4) adding the volume of polymer in 100 g of formulation tothe volume of hollow particles or pores in 100 g of formulation, todetermine the volume of 100 g of formulation; then 5) dividing thevolume of hollow particles or pores in 100 g of formulation by the totalvolume of 100 g of formulation and multiplying by 100 to give the volumepercent of pores or porosity in the formulation. The two methods willproduce similar values for volume percent porosity or pores, althoughthe second method will show lower values of volume percent pores orporosity than the first method where parameters during processing, suchas the reaction exotherm, can cause hollow polymeric particles ormicrospheres to expand beyond their nominal “expanded volume.” Because adecrease in pore size tends to increase polishing rate for a specificpore or porosity level, it is important to control the exotherm duringcasting to prevent further expansion of the pre-expanded hollowpolymeric particles or microspheres. For example, casting into a roomtemperature mold, limiting cake height, reducing prepolymer temperature,reducing curative amine temperature, reducing the NCO and limiting thefree TDI monomer all contribute to reducing the exotherm produced by thereacting isocyanate.

As with most conventional porous polishing pads, polishing padconditioning, such as diamond disk conditioning, serves to increaseremoval rate and improve wafer-scale nonuniformity. Althoughconditioning can function in a periodic manner, such as for 30 secondsafter each wafer or in a continuous manner, continuous conditioningprovides the advantage of establishing steady-state polishing conditionsfor improved control of removal rate. The conditioning typicallyincreases the polishing pad removal rate and prevents the decay inremoval rate typically associated with the wear of a polishing pad'ssurface. In particular, the abrasive conditioning forms a roughenedsurface that can trap fumed silica particles during polishing. FIGS. 1to 3 illustrate that silica particles can accumulate in the roughenedsurface adjacent the polishing pad's pores. This accumulation of silicaparticles into the polishing pad appears to increase the polishing pad'sefficiency by contributing to a high removal rate. In addition toconditioning, grooves and perforations can provide further benefit tothe distribution of slurry, polishing uniformity, debris removal andsubstrate removal rate.

Example

The polymeric pad materials were prepared by mixing various amounts ofisocyanates as urethane prepolymers with4,4′-methylene-bis-o-chloroaniline [MBCA] at 49° C. for the prepolymerand 115° C. for MBCA for examples of the invention (Comparative Examplesincluded 43 to 63° C. for the prepolymer). In particular, a certaintoluene diisocyanate [TDI] with polytetramethylene ether glycol [PTMEG]prepolymer provided polishing pads with different properties. Theurethane/polyfunctional amine mixture was mixed with the hollowpolymeric microspheres (EXPANCEL® 551DE20d60 or 551DE40d42 manufacturedby AkzoNobel) either before or after mixing the prepolymer with thechain extender. The hollow polymeric microspheres were either mixed withthe prepolymer at 60 rpm before adding the polyfunctional amine, thenmixing the mixture at 4500 rpm or were added to theurethane/polyfunctional amine mixture in a mixhead at 3600 rpm. Themicrospheres had a weight average diameter of 15 to 50 μm, with a rangeof 5 to 200 μm. The final mixture was transferred to a mold andpermitted to gel for about 15 minutes.

The mold was then placed in a curing oven and cured with a cycle asfollows: thirty minutes ramped from ambient temperature to a set pointof 104° C., fifteen and one half hours at 104° C. and two hours with aset point reduced to 21° C. Comparative Examples F to K used a shortercure cycle of 100° C. for about eight hours. The molded article was then“skived” into thin sheets and macro-channels or grooves were machinedinto the surface at room temperature—skiving at higher temperatures mayimprove surface roughness and sheet thickness uniformity. As shown inthe Tables, samples 1 to 2 represent polishing pads of the invention andsamples A to Z represent comparative examples.

TABLE 1 Hollow Nominal Polymeric Sphere NCO Stoichiometry SpheresDiameter Formulation Formulation (wt %) Prepolymer (%) (wt %) (um) 1MJK1859C 8.75-9.05 LF750D 85 3.36 20 2 MJK1859C 8.75-9.05 LF750D 85 3.3620 A S58 8.75-9.05 LF750D 85 2.25 40 B T58 8.75-9.05 LF750D 85 3.21 20 CS52 8.75-9.05 LF750D 105 0.75 40 D S53 8.75-9.05 LF750D 85 0.75 40 E T538.75-9.05 LF750D 85 1.07 20 F MJK3101A 11.4-11.8 Royalcast 85 3.01 202505 G MJK3101C 11.4-11.8 Royalcast 85 3.01 20 2505 H MJK3101B 11.4-11.8Royalcast 95 2.93 20 2505 I MJK3101D 11.4-11.8 Royalcast 95 2.93 20 2505J MJK1864A 11.4-11.8 Royalcast 105 2.86 20 2505 K MJK1864J 11.4-11.8Royalcast 105 2.86 20 2505 L MJK3122B 8.75-9.05 LF750D 85.00 3.87 20 MMJK3122F 8.75-9.05 LF750D 90.00 3.83 20 N MJK3122E 8.75-9.05 LF750D95.00 3.79 20 O MJK3122D 8.75-9.05 LF750D 100.00 3.74 20 P MJK3122A8.45-8.75 LF750D 105.00 3.70 20 Q MJK3122C 8.45-8.75 LF750D 110.00 3.6620 R VP3000 7.1-7.4 LF600D 85 1.8 40 S MJK1803C 8.75-9.05 LF750D 90.002.94 20 T MJK1803E 8.75-9.05 LF750D 90.00 2.94 20 U MJK1803A 8.75-9.05LF750D 115.00 2.94 20 V MJK1803F 8.75-9.05 LF750D 115.00 2.94 20 WMJK1803D 8.75-9.05 LF750D 90.00 2.20 20 X MJK1803H 8.75-9.05 LF750D90.00 2.20 20 Y MJK1803B 8.75-9.05 LF750D 115.00 2.20 20 Z MJK1803G8.75-9.05 115.00 2.20 20 Adiprene LF600D, LF750D and Royalcast 2505correspond to blends of toluene diiosocyanate and PTMEG productsmanufactured by Chemtura. LF600D and LF750D are low-free isocyanateprepolymers while Royalcast 2505 has high levels of free isocyanatemonomer.

Example polishing pads were tested on a Mirra® polisher from AppliedMaterials, Inc. using a platen rotation rate of 93 rpm, a wafer carrierhead rotation rate of 87 rpm and a downforce of 5 psi to polish TEOSsheet wafers. The polishing slurry was ILD3225 used as a 1:1 mixturewith DI water and supplied at the polishing pad surface a rate of 150ml/min. A Diagrid® AD3BG150855 conditioning disk was used todiamond-condition the polishing pad using an in situ conditioningprocess. TEOS sheet wafers were polished for 30 seconds or for 60seconds and each test with example pads also included wafers polishedwith the IC1010 pad as a baseline. The greatest importance was placed onthe 30 second polish rates relative to IC1010 because they would havethe greatest effect on reducing polishing times over the standardpolishing pad. The polishing results are below in Table 2.

TABLE 2 Hollow Nominal Polymeric Sphere RR at RR, RR at RR, SpheresDiameter 30 sec 30 sec 60 sec 60 sec Formulation Formulation (wt %) (um)(Å/min) norm (Å/min) norm NU, % Target >3750 ≧1.10 ≧4100 ≧1.08 <6.0 1MJK1859C 3.36 20 3778 1.18 4183 1.15 2.5 2 MJK1859C 3.36 20 3949 1.104235 1.08 5.7 A S58 2.25 40 3802 1.08 4263 1.10 3.0 B T58 3.21 20 40431.15 4414 1.17 2.8 C S52 0.75 40 3786 1.07 4070 1.04 5.5 D S53 0.75 403582 1.02 4043 1.01 3.4 E T53 1.07 20 3736 1.06 4175 1.05 3.1 F MJK3101A3.01 20 3303 0.94 3755 0.95 4.2 G MJK3101C 3.01 20 3123 0.89 3600 0.914.6 H MJK3101B 2.93 20 3162 0.90 3652 0.92 4.6 I MJK3101D 2.93 20 30870.88 3587 0.91 4.5 J MJK1864A 2.86 20 3180 0.91 3611 0.91 4.3 K MJK1864J2.86 20 3114 0.89 3583 0.91 5.4 L MJK3122B 3.87 20 3886 1.09 4219 1.076.0 M MJK3122F 3.83 20 3788 1.06 4050 1.03 6.0 N MJK3122E 3.79 20 37471.05 4079 1.04 11.4 O MJK3122D 3.74 20 3715 1.04 4015 1.02 7.8 PMJK3122A 3.70 20 3683 1.03 3915 1.00 7.1 Q MJK3122C 3.66 20 3450 0.973647 0.93 8.4 R VP3000 1.8 40 3330 0.80 2.3 S MJK1803C 2.94 20 3893 1.064219 1.03 3.2 T MJK1803E 2.94 20 4025 1.11 4251 1.05 7.6 U MJK1803A 2.9420 3803 1.03 4025 0.98 4.8 V MJK1803F 2.94 20 3673 1.01 3856 0.95 8.2 WMJK1803D 2.20 20 3688 1.00 4029 0.98 3.8 X MJK1803H 2.20 20 3692 1.013976 0.98 5.5 Y MJK1803B 2.20 20 3783 1.03 4053 0.99 4.6 Z MJK1803G 2.2020 3654 1.00 3859 0.95 7.6

These data indicate that a loading of 3.36 weight percent hollowpolymeric microspheres provided an unexpected increase in removal rate.In particular, Samples 1 and 2 had excellent removal rate at thirtyseconds and sixty seconds. The Sample 1 and 2 removal rates at thirtyseconds indicate that the polishing pad has high removal rate during anearlier part of a shortened polishing process that supports higherthroughput polishing. The comparative examples with 3.01 (2.94 for sameprepolymer) or of 3.66 weight percent and above resulted in a lowerremoval rate at thirty seconds and a lower overall removal rate. Inaddition, FIGS. 1 to 3 illustrate that the polishing pad's surfaceappears to trap fumed-silica in an advantageous location for polishing.This affinity to fumed silica appears to contribute to the increasedpolishing performance.

TABLE 3 Calculated # spheres in Calculated # Hollow Nominal cm³ spheresin cm³ Difference Polymeric Sphere formulation formulation in SpheresDiameter based on based on pad Calculated # Formulation Formulation (wt%) (μm) formulation density of Spheres Preferred >3.1 20 >9.25E+07 1MJK1859C 3.36 20 9.79E+07 9.50E+07 2.89E+06 2 MJK1859C 3.36 20 9.79E+079.34E+07 4.42E+06 A S58 2.25 40 1.18E+07 1.27E+07 −8.73E+05 B T58 3.2120 9.52E+07 1.05E+08 −9.55E+06 C S52 0.75 40 5.30E+06 5.95E+06 −6.53E+05D S53 0.75 40 5.30E+06 5.80E+06 −4.99E+05 E T53 1.07 20 4.25E+074.33E+07 −8.60E+05 F MJK3101A 3.01 20 9.21E+07 1.10E+08 −1.80E+07 GMJK3101C 3.01 20 9.21E+07 9.56E+07 −3.46E+06 H MJK3101B 2.93 20 9.04E+071.10E+08 −2.00E+07 I MJK3101D 2.93 20 9.04E+07 9.55E+07 −5.01E+06 JMJK1864A 2.86 20 8.90E+07 9.56E+07 −6.53E+06 K MJK1864J 2.86 20 8.90E+079.98E+07 −1.07E+07 L MJK3122B 3.87 20 1.07E+08 1.14E+08 −7.20E+06 MMJK3122F 3.83 20 1.06E+08 1.30E+08 −2.40E+07 N MJK3122E 3.79 20 1.05E+081.18E+08 −1.32E+07 O MJK3122D 3.74 20 1.04E+08 1.17E+08 −1.26E+07 PMJK3122A 3.70 20 1.04E+08 1.20E+08 −1.63E+07 Q MJK3122C 3.66 20 1.03E+081.22E+08 −1.92E+07 R VP3000 1.8 40 1.00E+07 2.98E+07 −1.98E+07 SMJK1803C 2.94 20 9.01E+07 9.21E+07 −2.02E+06 T MJK1803E 2.94 20 9.01E+071.06E+08 −1.60E+07 U MJK1803A 2.94 20 9.01E+07 1.07E+08 −1.68E+07 VMJK1803F 2.94 20 9.01E+07 1.17E+08 −2.70E+07 W MJK1803D 2.20 20 7.41E+076.82E+07 5.91E+06 X MJK1803H 2.20 20 7.41E+07 9.73E+07 −2.32E+07 YMJK1803B 2.20 20 7.41E+07 8.71E+07 −1.31E+07 Z MJK1803G 2.20 20 7.41E+079.45E+07 −2.04E+07

Table 3 illustrates that the hollow polymeric microspheres achieve aloading level in excess of one million microspheres per cubic centimeterof pad formulation.

Table 4 below shows prepolymer % NCO and compares mechanical strengthproperties of MBCA-cured elastomers, without filler or porosity, madefrom the prepolymers used in the example formulations as tested usingmethodology in ASTM D412. The tensile properties shown are defined inASTM D1566-08A. In addition, Table 4 shows the nominal density of theprepolymer cured with MBCA as reported by the prepolymer manufacturer.

TABLE 4 Tensile Tensile Tensile strength Stress at Stress at Nominalunfilled cured 100% 200% Polymer Prepolymer with MBCA, Elongation,Elongation, Density Prepolymer NCO (wt %) psi (MPa) psi (MPa) psi (MPa)(g/cm³) Adiprene 7.1-7.4 6700 (46.2) 3600 (24.8) 4800 (33.1) 1.16 LF600DAdiprene 8.75-9.05 7100 (48.9) 5300 (36.5) 5900 (40.7) 1.20 LF750DRoyalcast 2505 11.4-11.8 9200 (63)   — — 1.21

Table 4 illustrates that in addition to filler concentration, thepolishing pad's mechanical properties also appear to impact polishingperformance. Specifically, the polymer of Comparative Example R withLF600D appears to have inadequate stiffness, as best indicated by its100% modulus, for high removal rates for fumed silica polishing; andComparative Examples F to K made with Royalcast® 2505 quasi-prepolymer,which appears to be excessively stiff for high removal rates in fumedsilica polishing. Polyurethane materials cast from Royalcast 2505 wereso brittle that they broke prior to elongation at 100%.

In summary, the polishing pad is effective for polishing copper,dielectric, barrier and tungsten wafers. In particular, the polishingpad is useful for ILD polishing and in particular, ILD polishingapplications with fumed silica. The polishing pad has a rapid ramp toefficient polishing that provides a high removal rate at thirty seconds.The removal rate of polishing pads of the invention at both thirty andsixty seconds can exceed the removal rate of IC1000 polishing pads atthirty seconds and at sixty seconds. This rapid polishing response ofthe pads of the invention facilitates high wafer throughput incomparison to conventional porous polishing pads.

1. A polishing pad suitable for polishing patterned semiconductorsubstrates containing at least one of copper, dielectric, barrier andtungsten, the polishing pad comprising a polymeric matrix and hollowpolymeric particles within the polymeric matrix, the polymeric matrixbeing a polyurethane reaction product of a curative agent and anisocyanate-terminated polytetramethylene ether glycol at an NH₂ to NCOstoichiometric ratio of 80 to 97 percent, the isocyanate-terminatedpolytetramethylene ether glycol having an unreacted NCO range of 8.75 to9.05 weight percent, the curative agent containing curative amines thatcure the isocyanate-terminated polytetramethylene ether glycol to formthe polymeric matrix; and the hollow polymeric particles having anaverage diameter of 2 to 50 μm and a wt %_(b) and density_(b) ofconstituents forming the polishing pad as follows:$\frac{{wt}\mspace{14mu} \%_{a}*{density}_{b}}{{density}_{a}} = {{wt}\mspace{14mu} \%_{b}}$where density_(a) equals an average density of 60 g/l, where density_(b)is an average density of 5 g/l to 500 g/l, where wt %_(a) is 3.25 to4.25 wt %, the polishing pad having a porosity of 30 to 60 percent byvolume and a closed cell structure within the polymeric matrix forming acontinuous network surrounding the closed cell structure.
 2. Thepolishing pad of claim 1 wherein the continuous network forms aroughened surface upon conditioning with an abrasive; and the roughenedsurface is capable of trapping fumed silica particles during polishing.3. The polishing pad of claim 1 wherein the polishing pad has a Shore Dhardness of 44 to
 54. 4. The polishing pad of claim 1 wherein thepolishing pad has a porosity of 35 to 55 volume percent.
 5. Thepolishing pad of claim 1 wherein the hollow polymeric particles have anaverage diameter of 10 to 30 μm.
 6. A polishing pad suitable forpolishing patterned semiconductor substrates containing at least one ofcopper, dielectric, barrier and tungsten, the polishing pad comprising apolymeric matrix and hollow polymeric particles within the polymericmatrix, the polymeric matrix being a polyurethane reaction product of acurative agent and an isocyanate-terminated polytetramethylene etherglycol at an NH₂ to NCO stoichiometric ratio of 80 to 90 percent, theisocyanate-terminated polytetramethylene ether glycol having anunreacted NCO range of 8.75 to 9.05 weight percent, the curative agentcontaining curative amines that cure the isocyanate-terminatedpolytetramethylene ether glycol to form the polymeric matrix; and thehollow polymeric particles having an average diameter of 2 to 50 μm anda wt %_(b) and density_(b) of constituents forming the polishing pad asfollows:$\frac{{wt}\mspace{14mu} \%_{a}*{density}_{b}}{{density}_{a}} = {{wt}\mspace{14mu} \%_{b}}$where density_(a) equals an average density of 60 g/l, where density_(b)is an average density of 10 g/l to 300 g/l, where wt %_(a) is 3.25 to3.6 wt %, the polishing pad having a porosity of 35 to 55 percent byvolume and a closed cell structure within the polymeric matrix forming acontinuous network surrounding the closed cell structure.
 7. Thepolishing pad of claim 6 wherein the continuous network forms aroughened surface upon conditioning with an abrasive; and the roughenedsurface is capable of trapping fumed silica particles during polishing.8. The polishing pad of claim 6 wherein the polishing pad has a Shore Dhardness of 44 to
 54. 9. The polishing pad of claim 6 wherein thepolishing pad has a porosity of 35 to 50 volume percent.
 10. Thepolishing pad of claim 6 wherein the hollow polymeric particles have anaverage diameter of 10 to 30 μm.